Southwest engine explosion began when fan blade broke: NTSB

Federal air safety officials investigating why the engine of a Southwest Airlines jet blew apart, killing a passenger after shattering a plane window, said on Wednesday that the incident began when a fan blade already suffering metal fatigue snapped off in mid-flight. National Transportation Safety Board Chairman Robert Sumwalt told a news conference that he could not yet say if the incident, the first deadly airline accident in the United States since 2009, pointed to a fleet-wide issue in the Boeing 737-700. “We want to very carefully understand what was the result of this problem, and as I mentioned a few minutes ago, I’m very concerned about this particular event,” Sumwalt said at the news conference at the Philadelphia airport.